This invention relates to correction systems for controlling the quantity of intake air to an internal combustion engine in response to changes in atmospheric conditions.
For internal combustion engines, if the density of atmospheric air changes due to changes in weather conditions or changes in altitude, the air-fuel ratio introduced to the engine changes. This can result in deterioration of the performance of the engine and an increase in the level of pollutants in the engine exhaust gas, particularly when a vehicle is operated at high altitude. Because of this problem, various correction systems to adjust the volume of intake air for an engine in response to changes in operating altitude have been devised.
The devices and systems that have been developed generally fall into two categories. The first category comprises systems that vary the amount of fuel supplied to the engine. The second category comprises systems that vary the amount of a secondary air stream that is introduced to the engine. The first type of system has been found to have some disadvantages, including disruption of the operation of emission control systems dependent upon the amount of opening of the throttle valve.
In the second type of system, there is a prior art device that provides a by-pass in the venturi section of the air intake passage. The open cross-sectional area of the by-pass passage is varied in accordance with changes in atmospheric pressure.